Triazoles, such as benzotriazoles, tolyltriazoles, etc., are known to be useful as corrosion inhibitors, including for metal or metal alloy surfaces, synthetic detergents and antifreezes, as UV stabilizers, as intermediates in numerous syntheses such as, for example, dyes, and in water treatment applications. See, for example, U.S. Pat. Appln. No. 20010022424 (Vogt et al), published Jan. 28, 2010 (use of triazoles to reduce cobalt leaching); U.S. Pat. No. 8,236,204 (Matulewicz et al.), issued Aug. 7, 2012 (corrosion inhibiting composition comprising aliphatic-substituted tetrahydrobenzotriazoles solubilized in tetrahydrobenzotriazole activating solvents); and U.S. Pat. No. 8,236,205 (Matulewicz et al.), issued Aug. 7, 2012 (corrosion inhibiting composition comprising tetrahydrobenzotriazoles and/or other triazoles such as benzotriazoles and/or tolyltriazoles). For these triazoles to be suitable for certain applications and uses, it may be necessary for these triazoles to have a relatively high degree of purity. For example, discoloration may occur during the manufacture of these triazoles due to chemical oxidation of compounds, such as, for example, ortho-diaminotoluene, in making tolyltriazoles. Accordingly, it may be necessary to purify these triazoles, such as tolyltriazoles, prior to use as corrosion inhibitors, etc.
Suitable processes for purifying triazoles, such as tolyltriazoles and benzotriazoles, are known and described, collectively, for example, in U.S. Pat. No. 5,914,409 (Adkins et al.), issued Jun. 22, 1999. For example, when crude ortho-diaminotoluene is used as the reactant before starting diazotization and ring closure reaction in making tolyltriazoles, it may be necessary to purify the resulting tolyltriazoles. One method for purifying the resulting tolyltriazoles is by extracting the reaction mixture containing the tolyltriazoles with chloroform, washing the resulting chloroform solution, distilling off the chloroform, and then recrystallizing the crude tolyltriazole from benzene to obtain purified tolyltriazole. See U.S. Pat. No. 3,732,239 (Spatz et al.), issued May 8, 1973. Alternatively, the reaction mixture containing the triazole (with no intermediate isolation of the tolyltriazole prepared by diazotization and ring closure reaction) may be made alkaline by using aqueous sodium hydroxide solution, may be subjected to several clarifying filtrations, and may then be acidified (e.g., by using nitric acid) to a pH of from about 4.5 to 6 to cause precipitation and isolation of the purified tolyltriazole. See U.S. Pat. No. 3,970,667 (Gengnagel et al.), issued Jul. 20, 1976. See also GB Patent Specification 1,581,407 published Dec. 10, 1980, which discloses distilling off volatile components from the reaction mixture, and then recovering the triazole (e.g., benzotriazole) from the distilled mixture by crystallization.